Matched filter acting in charge domain

ABSTRACT

A charge mode operation circuit dedicated to detect the correlation between analog input signal and digital code, and for realizing by &#34;RAKE method&#34; the path diversity reception from the correlation data obtained using the same. The circuit utilizes an analog shift register using at least one charge transfer device for transferring a charge signal packet, a plurality of charge signal generation units, arranged along the analog shift register and provided, respectively, with substantially uniform voltage charge conversion characteristic controlled by a common input sign; and a routing mechanism for selectively transferring output charge packets generated by the plurality of charge signal generation units in given directions according to digital bit signal provided separately.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a matched filter acting in chargedomain which can be used for a communication apparatus, a signalprocessing equipment or the like.

2. Prior Art

As the result of digital technology development, CMDA (Code DivisionMultiple Access) communication or other digital modulation methods arebecoming popular rapidly; however the function required to the system isattaining such a high level that it can be hardly realized withconventional methods using digital processing in respect of system sizeor power consumption and this problem has became already evident inpower supply limited applications such as portable terminals.

As an approach for solving these problems, new methods introducinganalog processing such as Japanese Patent Laid-Open No. Hei 6-164320 arebeing developed, sloughing off ineffective power consumption inherent toconventional digital signal processing.

However, one can hardly affirm that these methods allow to realize alarge-scale analog shift register corresponding to future enlargement ofmodulation code, or to establish so far a technology which would be ableto correspond for a long term to commercialization constrictions such asfurther reduction of power consumption.

The present invention intends to compose a charge mode operation circuitdedicated to detect the correlation between analog input signal anddigital code using charge transfer devices such as CCD of whichtechnology is already established, famous for its low power consumption,and moreover, to propose a charge mode operation circuit composition forrealizing by "RAKE method" the path diversity reception from thecorrelation data obtained using the same.

SUMMARY OF THE INVENTION

The present invention has been made considering the view point asmentioned above, and its main invention intends to provide a matchedfilter acting in charge domain, comprising:

an analog shift register using at least one charge transfer device fortransferring charge signal packet;

a plurality of charge signal generation units, arranged along saidanalog shift register and provided respectively with substantiallyuniform voltage charge conversion characteristic controlled by a commoninput signal; and

a routing mechanism for selectively transferring output charge packetsgenerated by the plurality of charge signal generation units in givendirections according to digital bit signals provided separately;

wherein at least one of a plurality of output routs from said routingmechanism is connected to any of potential wells formed on said analogshift register, and in these potential wells, the addition in chargedomain of signals generated in said charge signal generation units andcharge signals transferred along the analog shift register fortransferring in synchronization therewith is executed.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a composition drawing showing a matched filter of anembodiment of the present invention.

FIG. 2 is a composition drawing showing a circuit connection equivalentto the case where the bit signal stored in the signal latch unit L shownin FIG. 1 is constant.

FIG. 3 is a composition drawing showing a matched filter of anotherembodiment of the present invention.

FIG. 4 is a composition drawing illustrating an example of RAKE typedemodulator, wherein differential output signal from the matched filterMF shown in FIG. 3 is supplied to a plurality of four quadrant MDACs(multiplication type DA converters) disposed on the prolongation of theanalog shift registers SR0, SR1, respectively executing multiplicationwith digital tap function value supplied separately, and synthesizingtheir results in differential form by two summing nodes SN0, SN1 toperform the path diversity modulation.

FIG. 5 is a composition drawing showing another example of RAKE typedemodulator.

FIG. 6 is a composition drawing showing an example of RAKE type signaldemodulator for demodulating signals, by installing two sets ofcomposition of FIG. 5 and taking as respective inputs orthogonal formtwo series of base band signals INI, INR.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an example of composition wherein charge signal packetsrespectively supplied from a plurality of charge signal generation unitsCG controled commonly by an input signal IN are supplied selectively toanalog shift registers SR using routing mechanisms R for determining itsoperation mode, namely its transfer rout according to bit signal ofmatching code supplied from a digital memory means M such as shiftregister and latched by signal latch units L, for executing additionoperation on said analog shift registers SR.

This example has a composition wherein only one of output from therouting mechanisms R is connected to the analog shift register SR andthe other output is not specially used and abandoned.

FIG. 2 illustrates a circuit connection equivalent to the case where bitsignals stored in the signal latch unit L as shown in FIG. 1 areconstant.

In this case, as the transfer direction of charge signal generated byindividual charge signal generation unit CG is always constant, therouting mechanism R is useless, and also charge signal destined to beabandoned needs not to be generated, so charge signal generation unitsother than a portion thereof need not to be installed, making thecircuit simpler, and moreover this composition will be extremelyadvantageous in respect of power consumption.

FIG. 3 illustrates a composition of the matched filter MF having acomposition similar to the example of FIG. 1, comprising two analogshift registers SR0, SR1 and obtaining a differential form matchingoutput using all respective two outputs from the routing mechanism R.

Naturally, such differential output generation can be realized with asingle analog shift register in the same way as that in FIG. 3 providedthat as much gates as necessary are disposed.

FIG. 4 illustrates an example of RAKE type demodulator, wherein adifferential output signal from the matched filter MF shown in FIG. 3 issupplied to a plurality of four quadrant MDACs (multiplication type DAconverters) disposed on the prolongation of the analog shift registersSR0, SR1, respectively executing multiplication with digital tapfunction value (not shown) supplied separately, and synthesizing theirresults in differential form by two summing nodes SN0, SN1 to performthe path diversity modulation.

Note that, as example of said MDACs, a MDAC of the type operating incharge domain, such as U.S. Pat. No. 5,539,404, is most appropriate;however, similar operation can be achieved also by an ordinary DAconverter naturally by using the conversion between charge and voltage.

In this example, while it is shown an example of executingmultiplication of digital tap function values using four quadrantmultiplication; when a matched filter supplying non differential formmatching output as shown in FIG. 1 is to be adopted, naturally the MDACsare only required to provide two quadrant multiplication function andoutput summing node also can be composed of a single one depending onthe conditions such as required accuracy or the like.

FIG. 5 is a composition diagram showing another embodiment of RAKE typedemodulator.

In FIG. 5, a multiplexer MPX multiplexes differential output of thematched filter by time-division multiplexing, and performs attenuationprocessing by a charge signal attenuator ATT, before supplyingrespective one of a plurality of four quadrant multiplication type MDACswith it as input signals.

On the other hand, the RAKE control unit "RAKE" supplies respectiveMDACs with digital form tap function values.

This RAKE control unit "RAKE", such as ordinary RAKE type demodulator,performs the function of identifying multi-path characteristics of acommunication line based on the matched filter output and individuallydetermining said tap function values according to the reliability ofindividual path.

In the case of this example, said tap function can be determined, forinstance, by measuring charge signal Aout abandoned by the charge signalattenuator ATT.

Naturally, said tap function can also be determined, outside theillustrated equipment, by more precise multi-path measurement data orthe like, obtained from the output, which is correlation-processed byanother matched filter unit, the signal, generally called sounder, setfor multi-path measurement included in reception signals.

FIG. 6 illustrates an example of RAKE type signal demodulator fordemodulating signal, by installing two sets of composition of FIG. 5 andtaking as respective inputs the orthogonal form two series of base bandsignals INI, INR.

In the composition of this example, the multiplexer MPX is supplied withoutputs from two matched filters, and, respectively as multiplexed, theyare attenuated by a charge signal attenuator ATT and then all added bycommon summing nodes SN0, SN1.

Here, as the RAKE control unit "RAKE" supplies respective MDACs with acoefficient obtained by multiplying a tap coefficient according to thereliability of each path with a phase compensation coefficient forcorrecting phase characteristics inherent to individual paths, itattenuates the effect of phase dispersion and variation of each pathcontained in the input and a stable output can be ensured.

Single chip type compact RAKE type modulator or the like can beconstructed by composing a small and low power consumption matchedfilter without using an active device, and using extremely low powerconsumption charge transfer device such as CCD and, moreover, by addinga product sum operation circuit acting in charge domain.

This allows to miniaturize and assure a longer battery life of portablecommunication gear of the communication method such as CDMA method usinglong code expected to be realized in the future.

What is claimed is:
 1. A RAKE type signal demodulator, comprising:amatched filter acting in charge domain, including,an analog shiftregister using at least one charge transfer device for transferring acharge signal packet, a plurality of charge signal generation units,arranged along said analog shift register provided, respectively, withsubstantially uniform voltage charge conversion characteristiccontrolled by a common input signal, and a routing mechanism forselectively transferring output charge packets generated by saidplurality of charge signal generation units in given directionsaccording to digital bit signal provided separately, wherein, at leastone of a plurality of output routs from said routing mechanism isconnected to any of potential wells formed on said analog shiftregister, and in these potential wells, the addition of signalsgenerated in said charge signal generation units and charge signalstransferred along said analog shift register for transferring insynchronization therewith is executed in charge domain; a plurality ofmultiplication type DA converters for selectively taking as an inputsignal the output signal packet composing time series of said matchedfilter and for executing multiplication with coefficient digital datasupplied separately; and at least one signal addition circuit foraddition-processing of outputs from said converters.
 2. The RAKE typesignal demodulator according to claim 1, wherein the number of saidanalog shift registers are two.
 3. The RAKE type signal demodulatoraccording to claim 1, wherein said digital bit signal is supplied by asignal latch unit disposed corresponding to said routing mechanism, andsaid signal latch unit stores the operation mode of said routingmechanism by selectively latching a matching code signal providedexternally.
 4. The RAKE type signal demodulator according to claim 2,wherein said digital bit signal is supplied by a signal latch unitdisposed corresponding to said routing mechanism, and said signal latchunit stores the operation mode of said routing mechanism by selectivelylatching a matching code signal provided externally.
 5. The RAKE typesignal demodulator according to claim 1, whereinsaid coefficient digitaldata is determined based on the past temporal change of the output fromsaid matched filter or a matched filter prepared separately.
 6. The RAKEtype signal demodulator according to claim 2, whereinsaid coefficientdigital data is determined based on the past temporal change of theoutput from said matched filter or a matched filter prepared separately.7. The RAKE type signal demodulator according to claim 3, whereinsaidcoefficient digital data is determined based on the past temporal changeof the output from said matched filter or a matched filter preparedseparately.
 8. The RAKE type signal demodulator according to claim 4,whereinsaid coefficient digital data is determined based on the pasttemporal change of the output from said matched filter or a matchedfilter prepared separately.
 9. The RAKE type signal demodulatoraccording to claim 3, for periodically updating digital bit signalsstored in said latch and for executing correlation detection whilefollowing the temporal change of the matching code.
 10. The RAKE typesignal demodulator according to claim 4, for periodically updatingdigital bit signals stored in said latch and for executing correlationdetection while following the temporal change of the matching code. 11.The RAKE type signal demodulator according claim 1, which is composed tospecify the function of said routing mechanism to the charge transferrespectively in given directions and to compute exclusively thecorrelation with fixed matching code.
 12. The RAKE type signaldemodulator according to claim 2 which is composed to specify thefunction of said routing mechanism to the charge transfer respectivelyin given directions and to compute exclusively the correlation withfixed matching code.
 13. A RAKE type signal demodulator comprising twomatched filter of any of claims 1-12; for computing the correlationtaking as respective inputs two series of base band signals includingindependent component, and for obtaining global output by adding, on acommon summing node output charged signal of multiplication result withdigital coefficient value provide separately.